Submission #1017164

#	Time	Username	Problem	Language	Result	Execution time	Memory
1017164		pavement	Longest Trip (IOI23_longesttrip)	C++17	100 / 100	14 ms	600 KiB

longesttrip

#include "longesttrip.h"
#include <bits/stdc++.h>
using namespace std;

#define pb push_back

mt19937 rng(42);

vector<int> perm;

bool my_are_connected(vector<int> v1, vector<int> v2) {
	for (auto &i : v1) {
		i = perm[i];
	}
	for (auto &i : v2) {
		i = perm[i];
	}
	return are_connected(v1, v2);
}

vector<int> longest_trip(int N, int D) {
	vector<int> ret;
	perm.resize(N);
	iota(perm.begin(), perm.end(), 0);
	shuffle(perm.begin(), perm.end(), rng);
	if (D == 3) {
		ret.resize(N);
		iota(ret.begin(), ret.end(), 0);
	} else if (D == 2) {
		deque<int> dq;
		int st = -1;
		dq.pb(0);
		if (my_are_connected({0}, {1})) {
			dq.pb(1);
			st = 2;
		} else {
			dq.pb(2);
			dq.pb(1);
			st = 3;
		}
		for (int i = st; i < N; i++) {
			if (my_are_connected({i}, {dq.back()})) {
				dq.pb(i);
			} else {
				dq.push_front(i);
			}
		}
		ret = vector<int>(dq.begin(), dq.end());
	} else {
		deque<int> ch1, ch2;
		ch1.pb(0);
		bool back_joined = 1;
		for (int i = 1; i < N; i++) {
			if (ch2.empty()) {
				ch2.pb(i);
				continue;
			}
			bool conn_to_1 = my_are_connected({ch1.back()}, {i});
			if (conn_to_1) {
				ch1.pb(i);
				back_joined = 1;
			} else {
				bool conn_to_2 = (!back_joined || my_are_connected({ch2.back()}, {i}));
				if (conn_to_2) {
					ch2.pb(i);
					back_joined = 0;
				} else {
					while (!ch2.empty()) {
						ch1.pb(ch2.back());
						ch2.pop_back();
					}
					ch2.pb(i);
					back_joined = 1;
				}
			}
		}
		vector<int> vec1(ch1.begin(), ch1.end()), vec2(ch2.begin(), ch2.end());
		if (vec2.empty()) {
			ret = vec1;
		} else {
			if (my_are_connected({vec1.back()}, {vec2.back()})) {
				for (int i = 0; i < (int)vec1.size(); i++) {
					ret.pb(vec1[i]);
				}
				for (int i = (int)vec2.size() - 1; i >= 0; i--) {
					ret.pb(vec2[i]);
				}
			} else if (my_are_connected({vec1[0]}, {vec2.back()})) {
				for (int i = (int)vec1.size() - 1; i >= 0; i--) {
					ret.pb(vec1[i]);
				}
				for (int i = (int)vec2.size() - 1; i >= 0; i--) {
					ret.pb(vec2[i]);
				}
			} else if (my_are_connected({vec1.back()}, {vec2[0]})) {
				for (int i = 0; i < (int)vec1.size(); i++) {
					ret.pb(vec1[i]);
				}
				for (int i = 0; i < (int)vec2.size(); i++) {
					ret.pb(vec2[i]);
				}
			} else {
				int lo = 0, hi = (int)vec1.size() - 1, idx1 = -1;
				while (lo <= hi) {
					int mid = (lo + hi) / 2;
					if (my_are_connected(vector<int>(vec1.begin(), vec1.begin() + mid + 1), vec2)) {
						idx1 = mid;
						hi = mid - 1;
					} else {
						lo = mid + 1;
					}
				}
				if (idx1 == -1) {
					if (vec1.size() > vec2.size()) {
						ret = vec1;
					} else {
						ret = vec2;
					}
				} else {
					assert(idx1 != -1);
					lo = 0, hi = (int)vec2.size() - 1;
					int idx2 = -1;
					while (lo <= hi) {
						int mid = (lo + hi) / 2;
						if (my_are_connected(vector<int>(vec2.begin(), vec2.begin() + mid + 1), {vec1[idx1]})) {
							idx2 = mid;
							hi = mid - 1;
						} else {
							lo = mid + 1;
						}
					}
					assert(idx2 != -1);
					// vec1[idx1] and vec2[idx2] are connected
					for (int i = (idx1 + 1) % (int)vec1.size(); i != idx1; i = (i + 1) % (int)vec1.size()) {
						ret.pb(vec1[i]);
					}
					ret.pb(vec1[idx1]);
					for (int i = idx2; (int)ret.size() != N; i = (i + 1) % (int)vec2.size()) {
						ret.pb(vec2[i]);
					}
				}
			}
		}
	}
	for (auto &i : ret) {
		i = perm[i];
	}
	return ret;
}

• Subtask 0: 0 / 0
• Subtask 1: 5 / 5
• Subtask 2: 10 / 10
• Subtask 3: 25 / 25
• Subtask 4: 60 / 60